The present invention relates to a method of simultaneously producing two continuous streams of cigarettes.
U.S. Pat. No. 4,336,812 relates to a cigarette manufacturing machine for simultaneously producing two continuous cigarette rods from a single paper strip, which is cut longitudinally into two substantially identical strips, which are fed, on respective side by side conveyor belts, along a rod forming beam and through a loading station where a respective stream of shredded tobacco is deposited on to each strip.
A major problem for ensuring correct operation of the above known machine is that of controlling the two conveyor belts so that they travel at substantially the same speed. In fact, by virtue of the paper strips of the two continuous rods on the above machine being cut from the same starting strip, any difference in the traveling speed of the two strips could result in at least one of them tearing.
Devices for controlling the speed of the conveyor belts have been devised, the proposed purpose being to detect, relatively rapidly, any difference in the speed of the conveyors, and accordingly act on the conveyors in such a manner as to eliminate the speed difference as rapidly as possible. In actual use, however, such devices have proved complex, expensive and unreliable.